A radio communication system based on LTE-Advanced (Long Term Evolution Advanced) for the 3GPP is presently being discussed. The possibility of expanding the transmission or reception frequency band of transmitted and received radio signals in the radio communication system based on LTE-Advanced by comparison with that in the LTE radio communication system is being discussed.
There is an aggregation as a technique for realizing such broadband transmission. For example, the aggregation involves aggregating a plurality of 20 MHz bands from among different frequency bands (800 MHz band, 3.5 GHz band, and the like) to obtain a bandwidth of 100 MHz, or aggregating a plurality of 20 MHz bands from the same frequency band to obtain a bandwidth of 100 MHz. For example, by transmitting data or the like by using the 100 MHz bandwidth, a base station apparatus can expand the bandwidth and realize faster transmission than in the case where the 20 MHz bandwidth is used.
On the other hand, how to handle a synchronization signal in the base station apparatus and a terminal apparatus in the case of realizing the broadband transmission by aggregation in the 3GPP is also being presently discussed. However, in a LTE-based radio communication system, the synchronization signal with a different sequence for each cell may be used.
Other conventional techniques relating to radio communication systems are described below, for example. Thus, the aggregation number of control channel elements in a downlink subframe corresponding to the ACK/NACK signal can be expanded over that of another downlink subframe.
In another technique, a AFC feedback control is performed based on the detected frequency error, a clock signal is generated with reference to the frequency of a reference signal, and the generated clock signal is supplied to an A/D conversion means, thereby shortening the lead-in time of frequency correction (synchronization).
Patent Document 1: Japanese Laid-open Patent Publication No. 2009-164815
Patent Document 2: Japanese Laid-open Patent Publication No. H11-234159
Non-Patent Document 1: 3GPPTS 36.211V8.8.0 (for example, 6.10.1.1, 6.11.1.1, 6.11.2.1)
Non-Patent Document 2: 3GPPTS 36.304V8.7.0 (for example, 5.2.3)
However, the aforementioned patent documents do not disclose the processing of the synchronization signal in the case where a plurality of bands is aggregated to perform broadband transmission.
Meanwhile, when broadband transmission is realized, the frequency accuracy or phase accuracy of the terminal apparatus can be degraded depending on the band in which the synchronization signal is used because a plurality of bands is aggregated to obtain a broad band.